Antimicrobial Drugs (NURS1059 2024-2025) – Review Flashcards

These flashcards cover core concepts, classifications, mechanisms of action, indications, adverse effects, interactions, and nursing considerations for antimicrobial drugs as outlined in the lecture notes.

What are the two possible effects of an antimicrobial agent on bacteria?

Bactericidal (kills) or bacteriostatic (inhibits growth).

Define sepsis and asepsis in the context of microbiology.

Sepsis is bacterial contamination; asepsis is the absence of significant contamination.

Why is bacterial cell-wall structure key to antibiotic mode of action (MOA)?

Because many antibiotics target the peptidoglycan cell wall, which differs between Gram-positive and Gram-negative bacteria and is absent in human cells.

How do Gram-positive and Gram-negative cell walls differ when Gram-stained?

Gram-positive walls are thick with peptidoglycan; Gram-negative have thinner peptidoglycan plus an outer membrane rich in lipopolysaccharides.

List the three sources of antibiotics.

Natural (fungal), semi-synthetic (chemically altered natural), synthetic (lab-designed).

Why do bacteria develop resistance faster to natural antibiotics?

They have been pre-exposed to these compounds in nature, selecting for resistance genes.

What inverse relationship exists as antibiotics progress from natural to synthetic?

Toxicity generally decreases while effectiveness increases.

Name the five functional MOA groups of antibiotics.

Inhibitors of cell wall synthesis, inhibitors of protein synthesis, inhibitors of membrane function, anti-metabolites, inhibitors of nucleic acid synthesis.

Which antibiotic class contains a β-lactam ring and what is its general MOA?

β-Lactams; they inhibit bacterial cell-wall synthesis.

Why are β-lactams selectively toxic to bacteria?

Humans lack peptidoglycan cell walls, the β-lactam target.

Give three shared advantages of β-lactam antibiotics.

Bactericidal, non-toxic, relatively inexpensive and water-soluble organic acids.

List four subclasses of β-lactams.

Penicillins, cephalosporins, carbapenems, monobactams (plus β-lactamase inhibitors).

What is the MOA of penicillins?

They interfere with synthesis of bacterial cell walls, leading to osmotic lysis.

Name four common infections treated with penicillins.

Otitis media, pneumonia, urinary tract infections, meningitis (also syphilis and gonorrhoea).

State two major adverse effects of penicillins related to electrolytes.

Hyperkalaemia and hypernatraemia (due to high potassium or sodium in formulations).

Which medications may interact with penicillins by increasing free active drug?

NSAIDs (displace penicillin from plasma protein binding sites).

How do cephalosporins differ across generations in Gram coverage?

Spectrum shifts from mainly Gram-positive (Gen 1) to broader Gram-negative (Gen 3-4) and MRSA/enterococci activity (Gen 5).

Give two common adverse effects of cephalosporins.

Diarrhoea and secondary infections (e.g., oral thrush or yeast infections).

Which substance can cause a disulfiram-like reaction with cephalosporins?

Alcohol (CIDLR: cephalosporin-induced disulfiram-like reaction).

What serious adverse event can carbapenems cause in some patients?

Drug-induced seizure activity.

For what tough infections is vancomycin commonly reserved?

MRSA and severe Clostridioides (Clostridium) difficile infections.

Describe ‘Red Man Syndrome’ associated with vancomycin.

An infusion-related histamine reaction causing pruritus, erythematous rash of face/neck/torso; managed by stopping infusion, giving antihistamine, then restarting slowly.

List three bacterial mechanisms of β-lactam resistance.

Reduced access to protein receptors, decreased receptor binding affinity, production of β-lactamase enzymes that destroy the drug.

What is the primary MOA of sulfonamide anti-metabolites?

They competitively inhibit folic-acid synthesis, blocking bacterial DNA production.

Why are sulfonamides selectively toxic to bacteria?

Humans obtain folic acid from diet rather than synthesizing it, so the pathway targeted is bacterial-specific.

What infection type is the classic indication for trimethoprim/sulfamethoxazole?

Urinary tract infections (also ear and respiratory infections).

Name two major drug interactions with sulfonamides.

Enhanced effects of warfarin and oral hypoglycaemic agents; increased methotrexate toxicity.

What is the MOA of aminoglycosides?

They bind bacterial ribosomes, inhibiting protein synthesis and leading to cell death (bactericidal).

Why must serum levels of aminoglycosides be monitored?

To minimise nephrotoxicity and ototoxicity, which are dose-related adverse events.

State two contraindications or cautions for aminoglycoside use.

Pregnancy and concurrent drugs that increase nephrotoxicity or reduce vitamin K (enhancing anticoagulant effect).

Which four antibiotic classes are grouped as MLSK?

Macrolides, lincosamides, streptogramins, ketolides.

When are macrolides often chosen over β-lactams?

When patients are allergic to β-lactams or for intracellular pathogens in soft-tissue or sexually transmitted infections.

What cardiac adverse event is associated with macrolides?

QT-interval prolongation, which can lead to arrhythmias.

How do tetracyclines inhibit bacteria, and why are they contraindicated in children under 8?

They bind to ribosomes blocking protein synthesis; in children they inhibit skeletal growth and discolour teeth.

Which common substances should not be taken with tetracyclines and why?

Milk, antacids, and iron supplements; divalent/trivalent cations form insoluble complexes reducing absorption.

What is the shared MOA of fluoroquinolones?

They inhibit bacterial DNA replication by targeting DNA gyrase and topoisomerase IV (bactericidal).

Name the five fluoroquinolones approved for use in Canada that students must know.

Ciprofloxacin, norfloxacin, ofloxacin, levofloxacin, moxifloxacin.

List two serious musculoskeletal or neurologic adverse events of fluoroquinolones.

Tendinopathy/tendon rupture (especially Achilles) and peripheral neuropathy.

Which electrolyte imbalances contraindicate fluoroquinolone use due to QT risk?

Uncorrected hypokalaemia or hypomagnesaemia.

What broad nursing step should occur before starting any antibiotic?

Collect microbiology specimens (e.g., blood, urine, wound swabs) for culture and sensitivity.

Provide two strategies nurses use to reduce antibiotic resistance.

Ensure correct antibiotic timing/dosage (e.g., pre-op prophylaxis) and educate patients about adherence and not demanding antibiotics for viral illnesses.

Why are β-lactams generally ineffective against Mycoplasma?

Mycoplasma lack a cell wall, so β-lactams have no target to inhibit.

Which β-lactamase inhibitors are commonly combined with penicillins to extend spectrum?

Clavulanic acid (e.g., amoxicillin/clavulanate) and tazobactam (e.g., piperacillin/tazobactam).

What class of antibiotics is considered ‘drugs of last resort’ for resistant Gram-positive infections like MRSA?

Glycopeptides (e.g., vancomycin).

Which aminoglycoside is still used for drug-resistant tuberculosis?

Streptomycin.

Describe the main difference between bactericidal and bacteriostatic drugs regarding immune reliance.

Bactericidal drugs kill bacteria directly, while bacteriostatic drugs halt growth and rely on host immune system to clear the infection.